NED Abstract 
Copyright by American Astronomical Society.
Reproduced by permission

2010ApJS..190...43H

Deep GALEX Observations of the Coma Cluster: Source Catalog and Galaxy
Counts

Hammer, D.; Hornschemeier, A. E.; Mobasher, B.; Miller, N.; Smith, R.;
Arnouts, S.; Milliard, B.; Jenkins, L.

Abstract. We present a source catalog from a deep 26 ks Galaxy Evolution
Explorer (GALEX) observation of the Coma cluster in the far-UV (FUV; 1530
A) and near-UV (NUV; 2310 A) wavebands. The observed field is centered
~0fdg9 (1.6 Mpc) southwest of the Coma core in a well-studied region of
the cluster known as "Coma-3." The entire field is located within the
apparent virial radius of the Coma cluster, and has optical photometric
coverage with Sloan Digital Sky Survey (SDSS) and deep spectroscopic
coverage to r ~ 21. We detect GALEX sources to NUV = 24.5 and FUV = 25.0,
which corresponds to a star formation rate of ~10^--3^ M_sun_ yr^--1^ for
galaxies at the distance of Coma. We have assembled a catalog of 9700
galaxies with GALEX and SDSS photometry, including 242 spectroscopically
confirmed Coma member galaxies that span a large range of galaxy types
from giant spirals and elliptical galaxies to dwarf irregular and
early-type galaxies. The full multi-wavelength catalog (cluster plus
background galaxies) is ~80% complete to NUV = 23 and FUV = 23.5. The
GALEX images presented here are very deep and include detections of many
resolved cluster members superposed on a dense field of unresolved
background galaxies. This required a two-fold approach to generating a
source catalog: we used a Bayesian deblending algorithm to measure faint
and compact sources (using SDSS coordinates as position prior), and used
the GALEX pipeline catalog for bright and/or extended objects. We
performed simulations to assess the importance of systematic effects
(e.g., object blends, source confusion, Eddington Bias) that influence the
source detection and photometry when using both methods. The Bayesian
deblending method roughly doubles the number of source detections and
provides reliable photometry to a few magnitudes deeper than the GALEX
pipeline catalog. This method is free from source confusion over the UV
magnitude range studied here; we estimate that the GALEX pipeline catalogs
are confusion limited at NUV ~ 23 and FUV ~ 24. We have measured the UV
field galaxy counts using our catalog and report a ~50% (30%) excess of
counts across FUV = 22-23.5 (NUV = 21.5-23) relative to other GALEX
studies. Our number counts are a better match to deeper UV galaxy counts
measured with Hubble Space Telescope. 

Key words: catalogs, galaxies: clusters: individual: Coma, galaxies:
statistics, techniques: photometric, ultraviolet: galaxies